The invention relates to connecting optical fibres and particularly to the management and routing of optical fibres at locations at which they are joined.
Typically in telecommunications, such joints are provided where it is desired to distribute optical fibres to customers. At the joint, optical fibres leading from a main, or primary network may be connected to fibres on a secondary network leading to individual customer locations. Hereinafter, fibres from the main network will be described as being supplied along a primary cable and as primary fibres, and fibres leading to customer locations will be described as secondary fibres. Such joints are usually provided under ground and may be accessed via a man-hole to enable connection work and routing to be carried out by an engineer.
Secondary optical fibres may be provided in enhanced performance fibre units (EPFU) which may comprise one or more fibres extending along a tube. The tube may be installed without optical fibres and when required, the optical fibres are blown through the tube using known techniques. Typically, the tubes are made from polyethylene and have a carbon loaded radially inner surface to increase conductivity. This helps to dissipate static charges developed during blowing which can hinder installation of the fibres along the tube.
Primary cables typically comprise a plurality of optical fibre bundles, or units, each bundle typically comprising eight or twelve fibres. At a joint location, the optical fibre bundles are separated and the individual optical fibres are managed and routed to housings, or splice trays, where they may be connected to secondary optical fibres leading to individual customer locations. An example of these housings or splice trays is disclosed in the assignee""s earlier application, U.S. Ser. No. 09/424,042, the content of which is incorporated herein by reference. Each housing comprises one port into which fibres may be routed from a primary cable and a second port into which secondary fibres may be routed from customer locations. Alternatively, the housings can be used to connect fibres from two primary cables.
FIGS. 1 and 2 illustrate schematically a joint arrangement 10 in which a plurality of housings 12, as disclosed in U.S. Ser. No. 09/424,042, are utilised for joining primary and secondary fibres. The arrangement comprises a stack of housings, or splice trays, 12 each of which has a first inlet port (not shown) and a second inlet port 13. Attached to the splice trays are two guide devices 14, each of which is associated with four splice trays.
The guide devices 14 each have an inlet arranged to receive a primary-side optical fibre bundle 16 containing a number of optical fibres and four outlets through which fibres are directed into respective inlet ports of the four housings associated with the guide device. Tracks (not shown) are provided for guiding the optical fibres between the inlet and the outlets.
As shown in FIG. 2, a primary fibre, or fibres 18, from the fibre bundle 16 is/are guided into a splice tray 12 to be spliced with a secondary fibre 20 to provide a part of a telecommunications circuit.
Generally, a primary cable contains more than one optical fibre bundle 16, for example, twelve bundles, which may each contain eight optical fibres making ninety-six optical fibres in total. Previously, two fibres were needed to allow communication at a customer locationxe2x80x94a first optical fibre transmitting light and a second optical fibre receiving light. Therefore, the exemplary primary cable having twelve optical fibre bundles with eight fibres in each may be connected to a joint arrangement for distribution to a maximum of forty-eight customer locations. Each customer is allocated at least one splice tray from which two secondary fibres lead to the customer location via the outlet port 13.
Recently, single fibre circuits have been introduced in which a single fibre both transmits and receives light. In this case, only a single primary and secondary fibre need be guided to each of the splice trays. The arrangement shown in FIGS. 1 and 2 does not readily permit the advantages of single fibre circuits to be obtained since the splice trays have only one outlet port, which does not provide for flexibility of fibre routing or the possibility of using spare capacity in the splice trays for routing new fibres into an existing installation converted from twin fibre to single fibre use.
It is an object of the invention to provide systems and assemblies for use in connecting optical fibres that can provide improved flexibility and choice in fibre routing.
It is another object of the invention to provide a method of and apparatus for routing additional optical fibres into a housing that is arranged to house joints between optical fibres.
It is a further object of the invention to provide methods of and apparatus for permitting additional optical fibres to be routed into the housings of existing optical fibre installations to permit advantage to be taken of single fibre circuits in place of twin fibre circuits.
The invention provides an assembly for use in connecting optical fibres, said assembly comprising a housing for optical fibre joints and a fibre routing device associated with said housing, said housing having a first inlet for receiving optical fibres from a primary side of an optical fibre network and a second inlet for receiving optical fibres from a customer side of an optical fibre network and defining pathways leading from said first and second inklets to an interior region of said housing that includes locating portions for locating optical fibre joints, and said fibre routing device having an insert portion axially insertable into said second inlet for locating and supporting the routing device relative to the housing at least two inlets for receiving optical fibres from said customer side of the optical fibre network and an outlet defined in said insert portion and connected with said routing device inlets such that fibres from said customer side of an optical fibre network received in said routing device inlets are routed into said second inlet of the housing via said routing device outlet.
The invention also provides a method of routing optical fibres to an optical fibre joint, said method comprising:
introducing at least one optical fibre from a primary side of an optical fibre network into a first of two inlets of a housing for optical fibre joints;
axially inserting an outlet end of a fibre routing device into a second of said two inlets such that an outlet of said fibre routing device feeds into said second inlet and said fibre routing device is located and supported relative to said housing by engagement between said outlet end and said second inlet, said fibre routing device having a plurality of entry points for optical fibres which entry points feed to said outlet; and introducing an optical fibre from a customer side of an optical fibre network into said housing by routing said optical fibre through a first of said entry points, said outlet and said second inlet of the housing.
The invention also provides an optical fibre installation comprising:
a plurality of housings for optical fibre joints arranged in a stack, said housings each having a first inlet for receiving optical fibres from a primary side of an optical fibre network, a second inlet for receiving optical fibres from a customer side of an optical fibre network and defining tracks for optical fibres leading from said first and second inlets to an interior region of said housing that includes locating portions for locating optical fibre joints;
a guide assembly for guiding optical fibres from said primary side of an optical fibre network into said housings, said guide assembly being mounted on said stack of housings and having at least one inlet port for receiving primary optical fibres and a plurality of outlet ports, each said outlet port being associated with a first inlet of one of said housings; and
a plurality of fibre routing devices, each said fibre routing device having an insert portion axially inserted into a said second inlet of a said housing such that the routing device is located and supported relative to said housing by interengagement between the second inlet of the housing and the insert portion of the routing device and an inlet end disposed externally of the housing and having at least two inlets for receiving optical fibres from said customer side of the optical fibre network, said at least two inlets being connected by passageways with an outlet defined in said insert portion such that optical fibres from said customer side of an optical fibre network received in said at least two inlets are routed into the said second inlet of the housing in which the insert portion is inserted via the routing device outlet.